Directionally controlled elastically deployable roll-out solar array

ABSTRACT

A directionally-controlled roll-out elastically deployable solar array structure is disclosed. The structure includes one or more longitudinal elastic roll out booms that may be closed section or open section to allow for efficient rolled packaging onto a lateral mandrel. A flexible photovoltaic blanket is attached to a tip structure and to a lateral base support structure, but remains uncoupled from the longitudinal booms. The solar array system may be stowed simultaneously into a rolled package comprised of the roll out booms and the flexible planar blanket together, or onto independent rolls. Alternatively, the system may be stowed by rolling the booms, and accordion Z-folding the hinged flexible photovoltaic blanket into a flat stack. Structural deployment is motivated by the elastic strain energy of the roll out booms, and several methods of deployment direction control are provided to ensure a known, controlled, and unidirectional deployment path of the elastically unrolling booms.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.13/010,739 which was filed on Jan. 20, 2011 for which application theseinventors claim domestic priority.

This invention relates to the field of solar arrays for space-basedapplications and, in particular, to flexible-blanket solar arraysdeployable from a spacecraft that are stowable in a small volume forshipment and launch. The U.S. Government may have rights in thisinvention pursuant to Contract. No. FA9453-08-M-0094.

FIELD OF THE INVENTION Background

A solar array, as defined herein, pertains to a structure which isstowable in a small volume for shipment and launch, and that isdeployable when in space to expose a large surface area of photovoltaiccollectors (solar cells) to the sun, and that is attached to certainspacecraft vehicles, to provide power for spacecraft operations. FIG. 1shows a typical spacecraft (101) that uses a solar array (102) for powerproduction, with the solar array (102) in the deployed configuration.

Solar arrays typically consist of an underlying structure for deploymentof a substantial number of individual photovoltaic solar cells from thebody of a spacecraft. Once fully deployed, it is desirable for the solararray structure to provide a lightweight, stiff, strong, stable and flatplatform for the solar cells to allow uniform exposure to the sun andminimize on-orbit spacecraft attitude control disturbance loads. Solararrays are typically stowed such that they are constrained in a smallenvelope prior to and during launch of the spacecraft and then aredeployed to their fully extended configuration, exposing the maximumarea of solar cells once the spacecraft has reached its position inouter space. It is desirable to minimize the volume of the stowedpackage while at the same time maximizing the available solar cell areathat can be packaged when stowed, and subsequently deployed to allow formaximum power production for the spacecraft.

In certain prior art applications of solar arrays, the structureconsists of flat rigid panel substrates that are configured for stowageby means such as hinges which will permit the panels to be foldedagainst each other to minimize the dimensions of the array in the stowedconfiguration. Folding of rigid panels involves mechanical items such ashinges and latches; and actuating mechanisms such as springs, cables andpulleys which must be highly reliable to prevent complete loss of aspacecraft and its payload due to inability to deploy thepower-producing array. These mechanical components are costly, andinvolve added weight which is desirable to minimize. An example of suchan array is shown in: Everman et al U.S. Pat. No. 5,487,791.

In order to allow for further reduction in the deployable solar arraysweight and stowed volume, the solar cell mounting can be configuredusing a flexible substrate, or blanket. Various flexible solar cellblanket substrates have been used, such as those fabricated from afiberglass mesh or thin polymeric sheet upon which are bonded thenumerous crystalline solar cells. Flexible-blanket solar arrays havebeen typically been limited to crystalline solar cell arrays packaged ina long roll or pleated stack that is deployed using a separatedeployment boom or hub structure requiring external motor power fordeployment motive force. These flexible array deployment structures havetypically consisted of very complex mechanical systems such as coilableor articulated truss booms, or radially oriented spars that rotate abouta central hub, which can add undesired parts, complexity, weight andcost to implement. Examples of prior art flexible blanket arrays areshown in the following United States patents: Harvey et al U.S. Pat. No.5,296,044; Stribling et al U.S. Pat. No. 6,983,914; Hanak et al U.S.Pat. No. 4,636,579 and Beidleman et al U.S. Pat. No. 7,806,370.

Critical to ensuring deployment reliability is to allow for maximumdeployment motive force (or torque) in the design of the deploymentactuators. Reliability is enhanced when the deployment actuation has alarge force margin (typically required to be at least 3:1) over any andall predicted (and unforeseen) sources of resistance to deployment, suchas harness bending, friction in joints, snagging or adhesive stickingbetween blanket layers. Historical solutions used to increase deploymentforce margin in a linearly deploying boom have been to increase the sizeand capability of structural components and use deployment actuators(such as springs or motors) to “force” the boom out, further increasingweight and complexity. An example of this sort of prior art is thebi-stem booms used on the Hubble telescope solar array to unfurl thesolar blankets. In this application, the booms are comprised of pairedcurled sheets of metal that are rolled and nest within one other to forma cylindrical boom upon deployment, and a complex and heavy motorizedmechanism is used to externally push the boom material out in a knowndeployment direction and with sufficient force. Utilizing the elasticstrain energy inherent in the deployment boom material alone to achievehigh deployment force has not been successfully used in the prior artfor deployable boom-type solar array structures. This is because inorder to raise the available actuation energy to levels sufficient toachieve acceptable deployment force margin, typical metallic orfiber-composite materials are too highly stressed (they are unacceptablyclose to failure), and the kinematics of deployment are difficult tocontrol and predict due to the high internal energy and ungovernednature of the stowed assembly upon release.

It is also desirable to maximize the deployed natural frequency(stiffness) and strength (against deployed accelerations) of a solararray. As the size of the solar cell deployed area and the solar arraysupporting structure increase, the stiffness of the solar cell arraydecreases and, as a result, the vibration frequency decreases anddisturbance deflections increase. The ability of the spacecraft attitudecontrol system to orient the spacecraft may be impaired if thedeflections due to low-frequency solar array movement are excessive.

A review of the prior art shows that significant efforts have been madeto reduce the weight and increase the deployment reliability and forcemargins of rigid and flexible blanket solar arrays for a given set ofdeployed stiffness and strength requirements. These prior efforts haveresulted in solar array designs tending to involve difficult and timeconsuming manufacturing, higher complexity and higher cost.

The current larger market for spacecraft is demanding significantdecreases in the cost of all spacecraft systems and payloads, includingsolar arrays. As the demand for spacecraft power grows, it is desirableto provide a deployable solar array system that permits straightforwardscaling up in size to allow use of larger deployed solar cell areas. Itis also desirable to enhance reliability, while at the same timereducing weight and cost, by reducing the number of component parts andmechanisms required to achieve deployment and adequate deployedperformance. Because mechanical components are subject to failure, andmust be rigorously tested as an assembled system to validate theirreliability; solar array reliability can be increased significantly,while simultaneously reducing cost and mass, by reducing the amount ofmechanical components and mechanisms required to deploy and form thearray into a deployed structure.

SUMMARY

The solar array of this invention has been greatly simplified relativeto the state of the art by significantly reducing the complexity andnumber of mechanical parts required for deployment of the solarcell-populated flexible blanket. The invention replaces complexdeployable mechanisms with a simple ultra-lightweight one-part tubularrolled boom structural element, that reliably elastically self-deploysunder its own strain energy and is directionally controlled such that itdeploys in a known, unidirectional manner without the need for heavy andcomplex auxiliary actuators to assist deployment or add deploy force.The boom structural element requires no hinges, dampers, complicatedsynchronization mechanisms, brakes, or motors for deployment, and doesnot have the parasitic mass associated with the mechanisms typicallyrequired by other prior art deployable solar array structures to achievehigh deployment force margin. Because the boom structure self-deployselastically via its own high internal strain energy, it does not requirepassive (solar) or active (via powered heaters) heating of the boommaterial to actuate deployment, and provides its owninternally-generated high deployment force. The available strain energyfor conducting deployment can be maximized to achieve the desireddeployment force margin by the use of a highly unidirectional thinfiber-composite layup material for the roll-out boom, because the boomcomponent of this invention is directionally controlled to always unrollin a known and predictable direction, without requiring a special (lowerdeployment force) bi-stable elastic laminate or elastic memory composite(EMC) material.

The invention also enables uniform stowage and secure packaging of thefragile solar cell-populated flexible blanket by maintaining a decoupledarrangement between the blanket longitudinal edges and the deploymentstructural elements, allowing either a rolled flexible photovoltaicblanket, or an accordion Z-folded flat-package arrangement to beimplemented when stowed; and allowing either simultaneous or independentdeployment of the boom structure and flexible blanket.

An elastic deployable boom system is disclosed. The boom systemcomprises one or more elastic roll out booms. Each roll out booms is athin-wall tubular, elongated structure, having a first end, a second endopposite the first end, and a longitudinal axis. The boom system has aboom mandrel, a yoke structure, and a deployment control device. Theboom mandrel, a substantially cylindrical structure, also has alongitudinal axis, as well as supporting structure operable for allowingthe mandrel to rotate about the longitudinal axis of the boom mandrel.The yoke support structure provides a fixed base for deployment of eachof the elastic roll out booms.

Each of the elastic roll out booms is attached at the first end to theboom mandrel and at the second end to the yoke structure such that thelongitudinal axis of the roll out boom is perpendicular to thelongitudinal axis of the boom mandrel. The elastic roll out boom crosssection can be flattened and rolled tightly around the boom mandrel toform a stowed roll. The stowed roll is operable for storing elasticstrain energy sufficient for powering deployment. The deployment controldevice is operable for controlling the elastic strain energy duringdeployment such that unidirectional deployment of each of the elasticroll out booms is assured.

One embodiment of the deployment control device includes a stabilizerbar, stabilizer arms, boom control rollers, a deployment lanyard and arotating pulley. The stabilizer arms connect the boom control rollers tothe longitudinal axis of the boom mandrel. The deployment lanyard has afirst end and a second end opposite the first end. The first end of thedeployment lanyard is attached to the stabilizer bar and the second endof the deployment lanyard is attached to the rotating pulley. Therotating pulley is attached to the yoke support structure such thatunidirectional boom deployment is effected.

A second embodiment of the deployment control device includes astabilizer bar, stabilizer arms, boom control rollers, and a rotarydamping mechanism. The rotary damping mechanism is connected in-linewith the mandrel axis and controls the rate of mandrel rotation duringdeployment. This, in turn, effects unidirectional boom deployment.

A third embodiment of the deployment control device includes stabilizerarms and boom control rollers, a frictionless tensioned containmentstrap, and a strap cross bar. The stabilizer arms connect the boomcontrol rollers to the longitudinal axis of the boom mandrel. Thefrictionless tensioned containment strap surrounds the stowed roll. Oneend of the containment strap is connected to the stabilizer bar, theother end is connected to the strap cross bar. The containment strapcontrols the rate of diameter reduction of the stowed roll duringdeployment which, in turn, effects unidirectional boom deployment.

The elastic deployable structure may include a flexible photovoltaicblanket. The flexible photovoltaic blanket is substantially planar,attached at one end to the boom mandrel, and at the opposite end to theyoke structure.

One embodiment of the elastic deployable structure includes a mandreloperable for simultaneous stowage of the elastic roll out booms and theflexible photovoltaic blanket. The elastic strain energy in the stowedarrangement is capable of powering simultaneous deployment of both theelastic roll out boom and the flexible photovoltaic blanket.

In a second embodiment of the elastic deployable structure is includedthe flexible photovoltaic blanket, a lateral blanket support structure,a base preload platen, and a tip preload platen. In this embodiment, theflexible photovoltaic blanket is operable for is stowage between the tippreload platen and the base preload platen as a z-fold flat package.Again, the elastic strain energy of the stowed roll is operable forpowering simultaneous deployment of both the elastic roll out boom andthe flexible photovoltaic blanket.

In a third embodiment of the elastic deployable structure is included aflexible photovoltaic blanket and a lateral blanket mandrel system. Thelateral blanket mandrel system comprises a lateral blanket mandrel, asystem of lanyards and pulleys, and an auxiliary electric motor. Here,deployment occurs in two stages. The elastic strain energy of the stowedroll is operable for powering initial deployment of the elastic roll outboom, while the lateral blanket mandrel system is operable for poweringsubsequent unrolling deployment of the flexible photovoltaic blanket.

In a fourth embodiment of the elastic deployable structure is included aflexible photovoltaic blanket, a base preload platen, a tip preloadplaten, and a lateral blanket mandrel system. The lateral blanketmandrel system comprises a lateral blanket mandrel, a system of lanyardsand pulleys, and an auxiliary electric motor. The flexible photovoltaicblanket is stowed between the tip preload platen and the base preloadplaten as a z-fold flat package. Again, deployment occurs in two stageswith the elastic strain energy of the stowed roll powering initialdeployment of the elastic roll out boom, and the lateral blanket mandrelsystem powering subsequent unfolding deployment of the flexiblephotovoltaic blanket.

Other desirable features and characteristics of the present inventionwill become apparent from the subsequent detailed description of theinvention and the appended claims, taken in conjunction with theaccompanying drawings and this background of the invention.

DESCRIPTION Glossary of Terms

Solar Array—A structure which is stowable in a small volume for shipmentand launch, and that is deployable when in space to expose a largesurface area of photovoltaic collectors (solar cells) to the sun, andthat is mechanically and electrically attached to a spacecraft vehicleto provide power for spacecraft operations

Flexible solar array—A solar array that includes a rollable or foldablethin flexible blanket or substrate to which the solar cells are mounted

Roll out boom—A thin-walled metallic or composite reinforced slit-tube(open section) or closed section hollow structural member. One or morebooms can be used as the primary longitudinal deployment and deployedstructural member of the solar array. The thin-walled elastic nature ofthe booms allow them to be flattened and rolled up into an extremelycompact stowage volume.

Elastic roll out boom—A roll out boom that that is constructed such thatit is self-deploying elastically though its own internal strain energy;and remains in the elastic state when rolled up. The elastic roll outboom does not require passive heating or active heating on thestructural tubular member to actuate deployment, and provides its ownsufficiently high deployment force. The available strain energy forconducting deployment may be maximized to achieve the requireddeployment force margin by the use of a primarily unidirectional thinfiber-composite laminate.

Deployment control—A method of restraining when rolled, and deploying anelastic roll out boom with a longitudinally-oriented unidirectional thincomposite layup so it unrolls in a known and predictable direction, withmaximum deployment torque, and without requiring a special (lowerdeployment force) bi-stable elastic laminate or elastic memory composite(EMC) material.

Directionally-controlled elastic roll out boom—A roll out boom that thatis constructed such that it is self-deploying elastically though its owninternal strain energy, remains in the elastic state when rolled up; andis directionally-controlled by incorporating one or more methods ofdeployment control so it unrolls in a known and unidirectional manner.

Mandrel—A hollow lightweight tube onto which the roll out booms and/orthe planar flexible PV blanket is rolled onto for compact stowage.

Flexible photovoltaic (PV) blanket—A thin flexible substrate that hasmounted to it an array of photovoltaic solar cells and associated wiringthat can be rolled or folded into a small package for stowage; and isattached to the deployable solar array structure (except for thelongitudinal booms) for unfurling into a flat, tensioned configurationduring deployment.

Yoke support structure—The lateral base structural support of the solararray onto which the longitudinal booms and flexible blanket areattached. Also can provide a mounting location for the standoff yokewhich can attach the solar array to the spacecraft body.

Batten—A lateral structural cross member that is attached between twolongitudinal roll out booms, but not attached to the flexible PVblanket; to provide added structural stiffness and/or strength to thedeployed solar array.

Stabilizer bar—A lateral member that spans across an elastic roll outboom mandrel, and can rotate about the mandrel axis; and providesmounting for the deployment control rollers and/or deployment rate limitlanyard

Blanket support structure—a lateral structural member that spans betweenthe two roll out boom mandrels and provides mounting interface for theleading edge of a roll out or Z-folded PV blanket during deployment andwhen fully deployed.

Preload platen (tip or base)—The rigid panels to which the tip and baseof an accordion Z-folded flexible PV blanket are attached, and whenfully stowed sandwich the one or more accordion Z-folded flexible PVblankets between the tip preload platen and the base preload platen inorder to preload and protect the fragile solar cells against damageduring launch vibratory loading.

Blanket unfurl lanyards—longitudinal chords or metal strips that deployout from a reel during initial elastic boom structure deployment of atwo-stage deployment system; after full deployment with the boomstructure, the blanket unfurl lanyards provide a known guide for thesubsequent unrolling (rolled) or unfolding (Z-fold) of the flexibleZ-fold blanket.

DESCRIPTION OF ITEMS IN THE FIGURES

-   101—Spacecraft (satellite) body: The primary structure to which the    solar array(s) are mounted to and provide power for; that carries    payloads and is launched into space.-   102—Deployed solar array wing: A structure which is stowable in a    small volume for shipment and launch, and that is deployable when in    space to expose a large surface area of photovoltaic collectors    (solar cells) to the sun, and that is attached to certain spacecraft    vehicles, to provide power for spacecraft operations.-   201—Directionally-controlled elastic roll out boom: A roll out boom    that that is constructed such that it is self-deploying elastically    though its own internal strain energy; and remains in the elastic    state when rolled up. The elastic roll out boom does not require    passive heating or active heating on the structural tubular member    to actuate deployment, and provides its own sufficiently high    deployment force. The elastic boom component is directionally    controlled to always unroll in a known and predictable direction    using one or more methods of deployment control such as boom control    rollers (507) and/or straps (701, 702). The available strain energy    for conducting deployment may be maximized to achieve the required    deployment force margin by the use of a primarily unidirectional    thin fiber-composite laminate.-   202—Yoke support structure: The lateral base structural support of    the solar array onto which the longitudinal booms (201) and flexible    blanket (204) are attached. Also can provide a mounting location for    the standoff yoke which can attach the solar array to, and provide    an offset from, the spacecraft body or gimbal.-   203—Mandrel: A hollow lightweight tube onto which the elastic roll    out booms (201) and/or the planar flexible PV blanket (204) is    rolled onto for compact stowage.-   204—Flexible Photovoltaic (PV) blanket: A thin flexible substrate    that has mounted to it an array of photovoltaic solar cells and    associated wiring that can be rolled or folded into a small package    for stowage; and is attached to the deployable solar array structure    for unfurling into a flat, tensioned configuration during    deployment.-   205—Blanket springs: Springs mounted to the flexible PV blanket    (204) lateral edge that allow the uncoupled flexible PV blanket    (204) to roll up at the same rate and diameter as the elastic roll    out booms (201) and be under uniform tension when fully deployed.-   301—Compressible open cell foam: Open-cell foam applied to the back    (non-cell populated) side of the flexible PV blanket (204) in    various forms such as strips, patches or continuous sheets. When the    blanket is rolled for stowage, the foam is compressed to take up the    differential spacing between the elastic boom roll diameter and the    blanket roll diameter so they remain the same. When fully compressed    in between the rolled (or Z-folded) flexible PV blanket layers in    the stowed configuration, the foam provides preload pressure and    damping to protect the fragile solar cells against damage during    launch vibratory loading.-   302—Mandrel ends: A component mounted to the mandrel (203) that    closes out the thin tubular section at the ends and that may provide    mechanical features that allow for the stowed elastic roll-out boom    (201) restraint during launch, and a mounting interface for bearings    located at the mandrel longitudinal axis of rotation.-   303—Launch tie bracket: Structural element mounted to the yoke    support structure (202) that reacts against the mandrel ends (302)    to locate and secure them tightly in the stowed configuration for    launch.-   304—Launch hold-down mechanism (or launch tie restraints): A    releasable device that preloads the mandrel ends (302) tightly    against a launch tie bracket (303) mounted to the yoke support    structure (202) in the stowed position. When the launch hold-down    mechanism (304) is released deployment of the solar array is    initiated.-   401—Batten: A lateral structural member that spans between deployed    elastic roll out booms (201), is uncoupled from the flexible PV    blanket (204), and when deployed may help to increase the deployed    structural strength and/or stiffness.-   501—Deployment lanyard: A cable, tape or strap that can be wrapped    around a pulley or spool and is paid out slowly with a rotary damper    (503), motor or other damping means to limit the rate of deployment    of the solar array.-   502—Deployment lanyard reel: A circular grooved pulley that allows    the deployment lanyard to roll up onto and extend from as it rotates    during deployment.-   503—Rotary damper: A rate-limiting device that limits the rotational    speed of the deployment lanyard reel (502) and corresponding    extension of the deployment lanyard to limit the rate of deployment    of the solar array.-   504—Mandrel axis: The longitudinal centerline axis of the mandrel    (203) about which it rotates during deployment.-   505—Stabilizer bar: Component that spans the width of the mandrel    (203) and is attached to the mandrel at its ends via mandrel    bearings (506) so that it can rotate about the mandrel axis (504).    Boom control rollers (507) may be attached to the stabilizer bar    (505) and positioned so that when the deployment lanyard (501) is    under tension due to the reaction of the elastic roll out boom (201)    deployment force, the boom control rollers (507) are preloaded by    the stabilizer bar (505) to provide localized loading throughout    deployment to assist in the required deployment control of each    elastic roll out boom (201).-   506—Mandrel bearings: Rotating bearings or bushings mounted to the    mandrel ends (302) and allow rotation of the mandrel (203) relative    to the stabilizer bar (505) about the mandrel axis (504).-   507—Boom control rollers: Component attached to the stabilizer bar    (505) and positioned so that when the deployment lanyard (501) is    under tension due to the reaction of the elastic roll out boom (201)    deployment force, the boom control rollers (507) are preloaded by    the stabilizer bar (505) against the roll out boom (201) underside    at a location nearly tangent to the rolled portion of the elastic    roll out boom (201). The preloaded boom control rollers (507)    provide localized loading throughout deployment to provide    deployment control of each elastic roll out boom (201).-   508—Stabilizer arm: A rigid rod that connects the stabilizer bar    (505) longitudinal axis with the boom mandrel axis (504) and allows    relative rotational motion between the stabilizer bar (505) and the    boom mandrel axis (504)-   601—Inter-wrap attachment strips: Hook and loop or other high    friction materials located on the opposing surfaces of the elastic    roll out boom (201); and that come into contact when the elastic    roll out boom is packaged by rolling and provide roll out boom (201)    deployment control.-   602—Open-section elastic roll out boom: An embodiment of the elastic    roll out boom whereby the circular boom cross section is broken by a    longitudinal slit that allows elastic flattening and subsequent    rolling for stowage.-   603—Roll out boom (201) inside surface: The interior surface of an    open-section roll out boom (602) onto which inter-wrap attachment    strips (601) are attached.-   604—Roll out boom (201) outer exposed surface: The exposed outer    surface of a rolled or unrolling elastic roll out boom (201), upon    which inter-wrap attachment strips (601) are attached, and to which    a radial load may be applied by a roller or strap to provide a means    of deployment control.-   605—Closed-section elastic roll out boom: An embodiment of the    elastic roll out boom whereby the boom cross section is continuous    and formed into a shape that allows elastic flattening and    subsequent rolling for stowage.-   606—Non-Controlled elastic roll out boom: An elastic roll out boom    that has no form of boom control implemented and therefore    “blossoms” upon release from the rolled state because adjacent    rolled layers are unconstrained to move in shear relative to each    other.-   701—Spring loaded sliding containment strap: External strap that    applies a radial load to constrain the stowed rolled boom layers    from “blossoming”, and assist in the required deployment control of    each directionally controlled elastic roll out boom (201). The strap    may consist of low-friction sliding materials that slide directly on    the directionally controlled elastic roll out boom (201) outer    exposed surface (604) during deployment.-   702—Spring loaded rolling containment strap: External strap that    consists of integral strap rollers (703) that allow the rolling    strap (702) to roll along the directionally controlled elastic roll    out boom (201) outer exposed surface (604) during deployment with    minimal friction.-   703—Integral strap rollers: Rolling elements integrated into a boom    control strap that allow it to roll with low friction on the boom    outer exposed surface (604)-   704—Strap tensioning springs: Springs utilized to apply tension to    the sliding (701) or rolling (702) straps as a means of providing    boom deployment control-   705—Strap cross bar: member that terminates in the strap (701, 702)    end and provides structural mounting for the strap tensioning    springs (704) that span between it and the stabilizer bar (505) to    apply the required strap tension.-   901—Mandrel, Boom mandrel: Same definition as (203) except as    applied to embodiment of FIG. 9; a mandrel upon which a single    directionally controlled elastic roll out boom (201) is rolled onto.-   902—Blanket support structure: A structure attached to each of the    boom mandrels (901) that spans between them and is located at the    tip of the array structure when deployed. The flexible PV blanket    assembly (204) may be attached to the deployable structural    subsystem at the lateral blanket support structure (902).-   903—Base preload platen: A rigid platen (such as made from honeycomb    panel) attached to the yoke support structure (202), that provides a    stiff and strong base for preloading a Z-folded PV blanket (204) and    foam (301) stack in conjunction with the tip preload platen (1001).-   904—Longitudinal blanket strips: Thin metal, composite or fabric    longitudinal blanket members that bend to allow hinge lines, and    stowage of the flexible PV blanket (204) in an accordion Z-folded    arrangement.-   905—SPMs: Solar cell-populated panel modules that may be constructed    of a lightweight substrate material such as Kapton, Kevlar, Glass    Epoxy or Graphite Epoxy to which the individual solar cells are    bonded and interconnected together into series strings to produce    the required electrical performance when illuminated by the sun.-   906—Outermost PV blanket SPM: Light weight rigid panel that serves a    dual purpose as an SPM solar cell substrate when deployed and a tip    preload platen (1001) when stowed, and when fully stowed forms a    flat-package comprised of a Z-folded flexible planar blanket (204)    that is sandwiched between the tip preload platen (1001) and the    base preload platen (903)-   1001—Tip preload platen: A rigid platen (such as made from honeycomb    panel) attached to the blanket support structure (902), that    provides a stiff and strong top plate for preloading a Z-folded PV    blanket (204) and foam (301) stack in conjunction with the base    preload platen (903).-   1101—Blanket stack launch tie down mechanism: Mechanism containing a    frangible bolt, or equivalent method release actuator; and    positioned to run through the Z-fold stack through holes provided    therein, or around the perimeter of the stack; and attached at the    base yoke support structure (202), to introduce a compressive    preload in the stowed Z-folded flexible PV blanket (204) and foam    (301) stack.-   1301—Blanket mandrel—Same definition as (203) except as applied to    the embodiment of FIG. 12; and used exclusively for rolling and    unrolling of the rolled flexible PV blanket (204) independent of the    elastic roll out booms (201).-   1302—Blanket mandrel bearings: Bearings located on the sides of the    blanket mandrel of embodiment of FIG. 12, and that allow independent    rotation of the blanket mandrel relative to the boom mandrel (901)    to enable a two-stage deployment (i.e. elastic boom (201) deployment    first, then flexible PV blanket (204) deployment second).-   1303—Blanket unfurl lanyards: Longitudinal chords or metal strips    that deploy out from a reel during initial elastic boom structure    deployment of a two-stage deployment system; after full deployment    with the boom structure, the blanket unfurl lanyards provide a known    guide for the subsequent unrolling (rolled) or unfolding (Z-fold) of    the flexible Z-fold blanket (907).-   1304—Lanyard pulley reels: A circular grooved pulley that allows the    blanket unfurl lanyards (1303) to roll up onto and extend from as it    rotates during deployment.-   1305—Lanyard pulley bearings: Bearings mounted to the lanyard pulley    reels (1304) that allow their rotation and paying out of the blanket    unfurl lanyards (1303).-   1306—Tip pulleys: A circular grooved pulley that allows the blanket    unfurl lanyards (1303) to roll up onto and over the tip of the array    structure, extending the blanket unfurl lanyards (1303) as the    blanket support structure (902) translates out with the booms (201)    and rotates during deployment.-   1401—Auxiliary electric motor: An electric motor that is mounted    such that it provides the motive torque to rotate the lanyard pulley    reels (1304) about the lanyard pulley bearings (1305), allowing the    blanket unfurl lanyards (1303) to be reeled onto their pulley reels    (1304) and subsequently unfurling the flexible PV blanket (204)    until fully deployed.

DESCRIPTION OF THE FIGURES

FIG. 1: is a perspective view of a typical spacecraft (101) that usesflexible solar arrays (102) for power production;

FIG. 2: is a perspective view of a solar array system in accordance withan exemplary embodiment of the present invention having twodirectionally controlled elastic roll out booms (201) and a singlerolled flexible photovoltaic (PV) blanket (204); in the fully deployedconfiguration;

FIG. 3: is a perspective view of a solar array system in accordance withan exemplary embodiment of the present invention having twodirectionally controlled elastic roll out booms (201) and a singlerolled flexible PV blanket (204); in the stowed packaged configuration;

FIGS. 4a, 4b, 4c : contains perspective views of a solar array system invarious stages of deployment; starting from fully stowed (FIG. 4a ), topartially-deployed (FIG. 4b ), to fully deployed (FIG. 4c ), inaccordance with an exemplary embodiment of the present invention;

FIG. 5: shows an embodiment of the invention that utilizes a deploymentlanyard (501) and rotary damper (502) system attached to the yokesupport structure (202) at the base and a stabilizer bar (504) at thetip for limiting deployment rate;

FIG. 6a : shows a rolled elastic boom with no form of deploymentcontrol, where upon release, the non-controlled boom (606) rolled layersare allowed to shear relative to one another and each progressive wrapthen expands in a radial direction (blossom); and the net direction ofdeployment is unknown.

FIG. 6b : shows the desired unrolling motion of a directionallycontrolled elastic roll out boom (201) in a known, unidirectional mannerthat is achieved with the implementation of a deployment control methodthat prevents relative shearing motion between the boom layers uponrelease.

FIG. 6c : shows an embodiment of the invention that uses facinginter-wrap attachment strips (601) of hook and loop or other highfriction materials on the opposing surfaces of the elastic roll out boom(201) to that provides high resistance to shearing between the rolledboom layers when stowed and throughout deployment as a means of elasticroll out boom (201) deployment control;

FIG. 7: shows an embodiment of the invention that uses external slidingor rolling spring-loaded straps (602) as a means of elastic roll outboom (201) deployment control;

FIG. 8: is a perspective view of a solar array system in accordance withan embodiment of the present invention having a single roll out boom(701) and two rolled flexible PV blankets (704); in the fully deployedconfiguration;

FIG. 9: a perspective view of a solar array system in accordance with anembodiment of the present invention having two elastic roll out booms(801) and a single Z-folded flexible PV blanket (807); in the stowed,deploying and fully deployed configurations;

FIG. 10: is a perspective view of a solar array system in accordancewith an exemplary embodiment of the present invention having two rollout booms (201) and a single Z-folded flexible blanket (204); in thestowed packaged configuration;

FIG. 11: is a perspective view of a solar array system in accordancewith an exemplary embodiment of the present invention having a Z-foldedflexible blanket stack (807); in the stowed packaged configuration; andhaving launch tie downs (1001) placed through the stack

FIG. 12: is a view of a solar array system in accordance with anexemplary embodiment of the present invention having a Z-folded flexibleblanket stack (907); in the stowed packaged configuration; and using thestowed restrained elastic roll out booms (201) and to apply the preloadforce.

FIG. 13: is a perspective view of a solar array system in accordancewith an exemplary embodiment of the present invention having two rollout booms and a single rolled flexible blanket; in the fully deployedconfiguration; and with independent deployment of elastic boom structureand rolled PV blanket from a blanket mandrel located at the base;

FIG. 14: solar array system in accordance with an exemplary embodimentof the present invention having two roll out booms and a single rolledflexible PV blanket; in the stages of deployment; and with independentdeployment of elastic boom structure and rolled PV blanket from ablanket mandrel located at the base;

FIG. 15: is perspective views of a solar array system in accordance withan embodiment of the present invention having two roll out booms and asingle Z-folded flexible PV blanket; in the various stages ofdeployment; and with independent deployment of elastic boom structureand Z-folded flexible PV blanket from a blanket flat package located atthe base;

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a typical spacecraft (101) that uses flexible solar arraysfor power production. A solar array (102) according to this inventionincludes one or more longitudinal elastic roll out booms (201); onelateral mandrel (203) or one or more lateral boom mandrels (901); one ormore lateral blanket attachment support structures (902), one basesupport yoke structure (202), one or more lateral battens (401), and oneor more planar flexible photovoltaic (PV) blankets (204) attached to thelateral mandrel (203) and base support yoke structure (202). Theflexible photovoltaic blankets (204) may be packaged in a rolled orZ-folded configuration and remain uncoupled to the elastic roll outbooms (201) along their longitudinal edges. The elastic roll out booms(201) may be comprised of closed sections or open sections that allowfor rolled packaging. Structural deployment is motivated by the elasticstrain energy of the one or more elastic roll out booms (201), and oneor more methods of deployment control are provided to ensure a straightand known unrolling deployment path of the one or more elastic roll outbooms (201).

One embodiment of the deployable solar array structural system (shown inFIGS. 2,3 and 4 a-c) is composed of two longitudinally-orientedthin-walled elastic roll out booms (201) that are attached togetherlaterally at the base to a yoke support structure (202) and laterally atthe tip to a mandrel (203). The mandrel (203) consists of a hollowlightweight tube onto which the roll out booms and the planar flexiblePV blanket (204) is rolled onto. The flexible PV blanket assembly (204)is attached to the deployable structural subsystem at the mandrel (tip)(203) and at the yoke support structure (root) (202) along theirrespective lengths, and may be attached rigidly, or withlongitudinally-oriented blanket springs (205) that allow the flexible PVblanket (204) to roll up at the same rate and diameter as the elasticroll out booms (201) and be under tension when fully deployed. To allowrolled packaging of the flexible PV blanket (204) into a diameter thatis the same as the rolled packaging of the roll out booms (201), and toallow deployment unrolling at the same rate and also to allow forindependent tensioning of the blanket to provide desired first modefrequency, the flexible PV blanket (204) is not attached (i.e.uncoupled) to the roll out boom (201) along its longitudinal length. Asshown in FIG. 3, compressible open cell foam (301), such as made frompolyimide material, is mounted to the back side (non-solar cellpopulated side) of the flexible PV blanket (204) in strips, patches oras a continuous sheet. When the flexible PV blanket (204) is rolled forstowage, the foam is compressed to take up the differential spacingbetween the elastic roll out boom (201) rolled diameter and the PVblanket (204) roll diameter so they remain the same. When fullycompressed in between the rolled flexible PV blanket (204) layers in thestowed configuration, the compressible foam (301) provides preloadpressure and damping to protect the fragile solar cells against damageduring launch vibratory loading.

When packaged in the stowed configuration for launch, the roll out boomsmay be restrained from elastically deploying by holding the mandrel ends(302) tightly against a launch tie bracket (303) mounted to the yokesupport structure (202) with a releasable strap, frangible boltmechanism, or other equivalent launch hold-down mechanism (304), asshown in FIG. 3. When the launch hold-down mechanism (304) is releasedto initiate deployment of the solar array, the roll out booms (201)elastically unroll. FIGS. 4a through 4c shows the solar array system ofthis embodiment in various stages of deployment; starting from fullystowed (FIG. 4a ), to partially-deployed (FIG. 4b ), to fully deployed(FIG. 4c ). The unrolling torque of the elastic roll-out booms (201)about the mandrel (203) axis (504), provide the motive force forlongitudinal deployment (unrolling) of the rolled flexible PV blanket(204).

The elastic roll out booms (201) may be either open section (slit tube)or closed section that allow flattening prior to and during rolling toenable a flat rolled packaging onto the mandrel (203). The elastic rollout booms (201) may be constructed from a fiber-reinforced composite,with a majority of the fibers directionally oriented along thelongitudinal axis of the roll out boom, or they may be of metallicconstruction. One or more lateral battens (401) may be attached to theroll out booms (201) to enhance the solar array deployed structuralstiffness and/or strength, but remain uncoupled to the flexible PVblanket (204) to allow independent blanket tensioning.

In one embodiment of the deployable solar array system, shown in FIG. 5,the elastic boom (201) unrolling may be limited in deployment rate bypaying out a deployment lanyard (501) longitudinally from deploymentlanyard reel attached (502) to a rate limiting device such as a rotarydamper (503) located on the yoke support structure (202). The rotarydamper (503) may alternately be located directly on the mandrel axis(504), allowing for elimination of the deployment lanyard (501).Alternatively, a motor and gear head arrangement may be used in place ofthe rotary damper to pay out the deployment lanyard (501) at a desiredrate. One end of the deployment lanyard (501) may be attached to astabilizer bar (505) that spans the width of the mandrel (203) and isattached to the mandrel (203) at its ends via perpendicular stabilizerarms (508) and mandrel bearings (506) so that it can rotate about themandrel axis (504).

Boom control rollers (507) may be attached to the stabilizer bar (505)and positioned so that when the deployment lanyard (501) is undertension due to the reaction of the directionally controlled elastic rollout boom (201) deployment force, the boom control rollers (507) arepreloaded by the stabilizer bar (505) against the directionallycontrolled roll out boom (201) underside at a location nearly tangent tothe outer unwrapping portion of the directionally controlled elasticroll out boom (201). The preloaded boom control rollers (507) providelocalized loading throughout deployment to assist in the requireddeployment control of each directionally controlled elastic roll outboom (201). The boom control rollers (507) may be used in combinationwith other methods of boom deployment control to further enhancedirectionally controlled elastic roll out boom (201) deployment control.

An alternate embodiment of the boom control rollers (507) is for thepreload to be provided by reacting the torque generated by dampedrelative rotation between the mandrel (203) and the stabilizer bar (505)about the mandrel axis (504). This torque is developed by the placementof a rotary damper at the mandrel axis (504) that limits relativerotational speed between the two, and allows elimination of thedeployment lanyard for deployment rate limiting.

In embodiments where the elastic roll-out booms (201) are constructedsuch that they are made of a reinforced fiber composite material ormetal, the material properties are such that the booms are not“bi-stable” in nature (i.e. they are highly unidirectional in thelongitudinal direction), and they remain linear elastic throughoutrolling and unrolling; they require one or more methods of boomdeployment control to so that the directionally controlled elastic rollout boom (201) unrolls in a known, straight and predictable direction.The boom deployment control is required to prevent “blossoming” radiallydue to unrestrained shear displacement between rolled layers, as shownin FIG. 6a where upon release, the non-controlled boom (606) rolledlayers are allowed to shear relative to one another and each progressivewrap then expands in a radial direction; and the net direction ofdeployment is unknown. FIG. 6b shows the desired unrolling motion of adirectionally controlled elastic roll out boom (201) in a known,unidirectional manner that is achieved with the implementation of adeployment control method that prevents relative shearing motion betweenthe boom layers upon release. As shown in FIG. 6c , a method forachieving the necessary elastic roll out boom (201) deployment controlis to apply a material that provides high resistance to shearing betweenthe rolled boom layers when stowed and throughout deployment, such asfacing inter-wrap attachment strips (601) of hook and loop or other highfriction materials on the opposing surfaces of the directionallycontrolled elastic roll out boom (201); and that come into contact whenthe elastic roll out boom is packaged by rolling. As shown in FIG. 6,for an open-section elastic roll out boom (602) one half of theinter-wrap attachment strip is attached longitudinally to the insidesurface (603) and the opposing half is attached longitudinally to theoutside surface (604) so that they come into high-friction contact whenthe open section elastic roll out boom is flattened and rolled,preventing shear motion (and resultant “blossoming”) during unrollingdeployment. For the embodiment using a closed-section elastic roll outboom (605), one half of the inter-wrap attachment strip is attachedlongitudinally to the outside surface (604) and the opposing half isattached to the opposing outside surface (604) so that they come intohigh-friction contact when the open section elastic roll out boom isflattened and rolled, preventing shear motion (and resultant“blossoming”) during unrolling deployment.

Boom control rollers (507) may be used as previously described and incombination with the inter-wrap attachment strips (601) to furtherenhance roll out boom (201) deployment control.

In another embodiment of the invention shown in FIG. 7, deploymentcontrol of the roll out booms (201) may be accomplished with an externalspring-tensioned sliding containment strap (701) or rolling containmentstrap (702) that applies a radial load to constrain the rolled boomlayers from “blossoming”, and assist in the required deployment controlof each elastic roll out boom (201). The external sliding containmentstrap (701) or rolling containment strap (702) may be used incombination with the inter-wrap attachment strips (601) to furtherenhance roll out boom (201) deployment control. The strap may consist oflow-friction sliding materials that slide directly on the roll out boom(201) outer exposed surface (603) during deployment. Alternatively thestrap may consist of integral rollers within the strap (703) that allowthe rolling containment strap (702) to roll along the roll out boom(201) outer exposed surface (603) during deployment with minimalfriction. The containment strap (701, 702) is pulled radially tightaround the rolled elastic boom (201) outer exposed circumference (603)with strap tensioning springs (704) that provide sufficient straptension to allow boom containment and deployment control. The strap maybe terminated on one end with a strap cross bar (705) that also providesa structural mounting for the strap tensioning springs (704) that spanbetween the cross bar (705) and the stabilizer bar (505) to apply therequired strap tension.

Another embodiment of the deployable solar array structural system(shown in FIG. 8) is composed of a single longitudinally-orientedthin-walled elastic roll out boom (801) that is attached at the base toa yoke support structure (802) and at the tip to a lateral mandrel(803). The mandrel (803) consists of a hollow lightweight tube ontowhich the roll out boom (801) and the two planer flexible PV blankets(804) are rolled. The flexible PV blanket assemblies (804) are eachattached to the deployable structural subsystem at the mandrel (803) andat the yoke support structure (802) along their respective ends, and maybe attached via blanket springs (805) to allow for tensioning of theblanket when fully deployed. In order to allow rolled packaging of theflexible PV blankets (804) into diameters that are the same as therolled packaging of the roll out boom (801), and to allow deploymentunrolling at the same rate; the flexible PV blankets (804) are notattached (i.e. uncoupled) to the elastic roll out boom (801) along itslongitudinal length.

Another embodiment of the deployable solar array structural system(shown in FIG. 9) is composed of two longitudinally-oriented thin-walledelastic roll out booms (201). The elastic roll out booms (201) areattached together laterally at the base to a yoke support structure(202) and laterally at the tip to two boom mandrels (901), consisting ofa hollow lightweight tube onto which each roll out boom (201) isindividually rolled onto. A lateral blanket support structure (902) isattached to each of the boom mandrels (901) and spans between them. Theflexible PV blanket assembly (204) is attached to the deployablestructural subsystem at the lateral blanket support structure (902) andat a base preload platen (903) attached to the yoke support structure(202) along their respective lengths, and may be attached withlongitudinally-oriented blanket springs (205) that allow the flexible PVblanket (204) to be under tension when fully deployed. The flexible PVblanket (204) is hinged, or is manufactured from thin metal, compositeor fabric longitudinal strips (904) that bend to allow hinging, andstowage in an accordion Z-folded arrangement, whereby adjacent discretesolar cell populated panel modules (or SPMs, 905) remain flat and foldup so their front side surfaces are face-to-face and their rear sidesurfaces are face-to-face when in the fully stowed flat-packagedconfiguration. The SPMs (905) may be constructed of a lightweightsubstrate material such as Kapton, Kevlar, Glass or Graphite Epoxy towhich the individual solar cells are bonded and interconnected togetherinto series strings to produce the required electrical performance whenilluminated by the sun. The single outermost PV blanket SPM (906) may becomprised of a light weight rigid panel, such as honeycomb with thinface sheets, that serves as an SPM solar cell substrate (906) whendeployed.

As shown in FIG. 10, the single outermost PV blanket SPM (906) comprisedof a light weight rigid panel, serves a dual purpose as an SPM (905)solar cell substrate when deployed and a tip preload platen (1001) whenstowed, and when fully stowed forms a flat-package comprised of aflexible PV blanket (204) that is folded and sandwiched between the tippreload platen (1001) and the base preload platen (805) in order topreload and protect the fragile solar cell-populated SPMs (905) againstdamage during launch vibratory loading. The flexible PV blanket SPMs(905) may have compressible open cell foam (301) attached to the backside (opposite the solar cells) in strips, patches or continuous sheetsas required to provide cushioning and damping between the preloadedflexible PV blanket (204) layers and tip preload platen (1001) and basepreload platen (905) for enhanced solar cell protection.

In one embodiment of the Z-fold solar array system, shown in FIG. 11,the fully stowed Z-folded flexible PV blanket (204), foam (301) and tipplaten (1001) and base preload platen (903) stack may be preloadedtogether at one or more locations with a blanket stack launch tie downmechanism (1101). The blanket stack launch tiedown mechanism (1101) mayconsist of a frangible bolt, or equivalent release actuation method,positioned to run through the tip/base preload platens (1001, 903),stowed blanket (204) and foam (301) stack through holes provided for theblanket stack launch tie downs (1101), or around the perimeter of thestack. The blanket stack launch tie downs (1101) may be attached(grounded) at the base yoke support structure (202), to introduce acompressive preload in the stowed Z-folded flexible PV blanket (204)stack.

In another embodiment of the Z-fold system shown in FIG. 12, the stowedand restrained booms (201) are located such that they themselves applythe desired compressive preload force to the flexible PV blanket stacklayers (204), tip preload platen (1001) and base preload platen (903).This is accomplished by locating the lateral blanket support structure(902) so it directly bears on the tip platen (1001) via a snubberbracket (1201) that is rigidly attached to the tip platen (1001) whenstowed, to provide PV blanket stack (204) preload for enhanced solarcell protection and to minimize stowed packaging volume. The snubberbracket (1201) is contoured so that it nests with the outer diameter ofthe lateral blanket support structure (902), and the lateral blanketsupport structure (902) is tightly held by the launch hold-downmechanism (304). Upon release of the launch hold-down mechanism (304)and deployment, the lateral blanket support structure (902) can pullaway from the snubber bracket (1201).

Another embodiment of the deployable solar array structural system usinga rolled flexible PV blanket, shown in FIG. 13, consists of thedeployable structure previously described comprising of two longitudinalroll out booms (201); two lateral boom mandrels (901) and a lateralblanket support structure (902) which is attached to each of the boommandrels (901) and spans between them. A separate flexible PV blanketmandrel (1301) is located at the base and is centered between theelastic roll out booms (201) and attached to the base support yokestructure (202) via blanket mandrel bearings (1302) that allow it torotate independently. In this unique embodiment, the rolled solar arrayassembly is stowed by rolling the two elastic roll out booms (201) andthe flexible PV blanket (204) onto their own separate, independentmandrels (901), (1301). The tip end of the rolled flexible PV blanket(204) is attached to a plurality of blanket unfurl lanyards (1303) thathave their opposite ends attached to lanyard pulley reels (1304) thatare attached to the yoke support structure and allowed to rotate vialanyard pulley bearings (1305) and pay out or reel in the blanket unfurllanyards (1303). The blanket unfurl lanyards are looped around tippulleys (1306) located on the lateral blanket support structure (902).Restraint of the elastic roll out booms (201) in the stowedconfiguration for launch may be achieved in a manner as previouslydescribed, via boom launch tie restraints (304). Rolling and preload ofthe rolled flexible PV blanket (204) using open cell foam (301) isachieved in a manner as previously described. The rotation of theflexible PV blanket mandrel (1301) is restrained for launch at its endssimilar to a method previously described for the boom launch restraints.

The deployment of this embodiment is performed in two stages, as shownin FIG. 14. In the first stage, the boom launch tie restraints (304) arereleased and the independent deployment of the roll out boom structureis motivated through elastic strain energy-driven unrolling of theelastic roll out booms (201). One or more methods of deployment controlpreviously described (see FIGS. 6 and 7) are utilized to ensure astraight and known deployment path of the elastic roll out booms (201).Simultaneously with the elastic boom deployment, the blanket unfurllanyards (1303) are paid out from the lanyard pulley reels (1304)longitudinally with the linear motion of the lateral blanket supportstructure (902) until full extension of the elastic booms (201) andblanket unfurl lanyards (1303) is achieved. In the second stage ofdeployment, the subsequent independent unrolling deployment of therolled flexible PV blanket (204) is motivated through an auxiliaryelectric motor (1401) that is attached to the lanyard pulley reels(1304); and by reversing the direction of the lanyard pulley reel's(1304) rotation to reel in the blanket unfurl lanyards (1303) back ontotheir respective lanyard pulley reels (1304), simultaneously extendingout (unfurling) the flexible PV blanket (204) by unrolling it from itsblanket mandrel (1301) until it is fully deployed, planar and undertension. In order to allow separate deployment unrolling of the flexiblePV blanket (204) that is independent of the elastic roll out booms(201), the flexible PV blanket (204) is not attached (i.e. uncoupled) tothe roll out booms (201) along its two longitudinal edges.

In another embodiment of the deployable solar array structural systemusing a Z-fold flexible PV blanket (204), shown in FIG. 15, thedeployable structure previously described comprising of two longitudinalroll out booms (201); two lateral boom mandrels (901) and a lateralblanket support structure (902) which is attached to each of the boommandrels (901) and spans between them. A separate base preload platen(903) is located at the base and is centered between the elastic booms(201) and attached to the base support yoke structure (202). In thisembodiment, the roll out booms (201) and the remaining solar arraystructure is stowed by rolling the two elastic roll out booms (201) ontotheir own separate, independent mandrels (901), and by simultaneouslypackaging the flexible PV blanket (204) in an accordion Z-foldedarrangement, whereby adjacent discrete hinged solar cell populated panelmodules, or SPMs (905) remain flat and fold up so their front sidesurfaces are face-to-face and their rear side surfaces are face-to-facewhen in the fully stowed flat-packaged configuration, as shown in FIG.15. The single outermost PV blanket SPM (906) is comprised of a lightweight rigid panel, such as honeycomb with thin face sheets, that servesa dual purpose as an SPM (905) solar cell substrate when deployed and atip preload platen (1001) when stowed. When fully stowed a flat-packagestack is formed, comprised of the Z-folded flexible PV blanket (204)that is sandwiched between the tip preload platen (1001) and the basepreload platen (903) in order to preload and protect the fragile solarcells against damage during launch vibratory loading. The flexible PVblanket (204) may have compressible open cell foam (301) attached to theback side (opposite the solar cells) in strips, patches or continuoussheets as required to provide cushioning and damping between thepreloaded PV blanket (204) layers and tip/base platens (1001), (903) forenhanced solar cell protection.

The tip preload platen is attached to a plurality of blanket unfurllanyards (1303) that have their opposite ends attached to lanyard pulleyreels (1304) that are attached to the yoke support structure (202) andallowed to rotate via pulley bearings (1305) and pay out the blanketunfurl lanyards (1303). The blanket unfurl lanyards (1303) may be loopedaround tip pulleys (1306) located on the lateral blanket support (902).Restraint of the elastic roll out booms (201) in the stowedconfiguration for launch may be achieved with boom launch hold-downs(304) in a manner as previously described. The restraint for launch ofthe preloaded flexible PV blanket (204) and tip/base platens (1001),(903) may be performed using blanket stack launch tie downs (1101)similar to methods previously described. The deployment of thisembodiment is performed in two stages, as shown in FIG. 15. In the firststage, the boom launch tie restraints (304) are released and theindependent deployment of the elastic roll out booms (201) is motivatedthrough elastic strain energy-driven unrolling of the roll out booms(201); and one or more methods of deployment control previouslydescribed are utilized to ensure a straight and known deployment path ofthe elastic roll out booms (201). Simultaneously with the elastic boomroll out boom (201) deployment, the blanket unfurl lanyards (1303) arepaid out from the lanyard pulley reels (1304) longitudinally with thelinear motion of the lateral blanket support structure (902) until fullextension of the elastic roll out boom (901) structure and blanketunfurl lanyards (1303) is achieved. In the second stage of deployment,the subsequent independent unfolding deployment of the Z-folded flexiblePV blanket (204) is motivated through an auxiliary electric motor (1401)that is attached to the lanyard pulley reels (1304). By reversing thedirection of the lanyard pulley reel's (1304) rotation to reel in theblanket unfurl lanyards (1303) back onto their respective lanyard pulleyreels (1304), the Z-folded flexible PV blanket (204) is simultaneouslyextended by unfolding it until it is fully deployed, planar and undertension. In order to allow separate deployment unfolding of the flexiblePV blanket (204) that is independent of the elastic roll out booms(201), the flexible PV blanket (204) is not attached to (i.e. uncoupledfrom) the roll out booms (201) along its two longitudinal edges.

The invention claimed is:
 1. A deployable structure comprising: anelastic roll out boom comprising: a thin-wall tubular, elongatedstructure, of a fiber-composite layup material having internal strainenergy, the elastic roll out boom having a stowage configuration fortransport and a deployed configuration in which the elastic roll outboom is fully extended, the elastic roll out boom having a first end, asecond end opposite said first end, wherein a longitudinal axis isdefined by the first end and the second end when the elastic roll outboom is in the deployed configuration, wherein only the internal strainenergy of the fiber-composite layup material causes extension of theelastic roll out boom from the stowage configuration to the deployedconfiguration without passive or active heating of the fiber-compositelayup material.
 2. The deployable structure of claim 1 wherein thefiber-composite layup material is primarily unidirectional.
 3. Thedeployable structure of claim 1 further comprising a mandrel, themandrel being a substantially cylindrical structure having alongitudinal axis upon which the mandrel is able to rotate, wherein thelongitudinal axis of the elastic roll out boom is perpendicular to thelongitudinal axis of the mandrel, and the elastic roll out boom iscapable of being reversibly flattened in cross-section and rolled uponthe mandrel into the stowage configuration.
 4. The deployable structureof claim 3 further comprising a yoke support structure, the yoke supportstructure providing a fixed base for deployment of the elastic roll outboom, wherein the first end of the elastic roll out boom is attached tothe mandrel and the second end is attached to the yoke supportstructure.
 5. The deployable structure of claim 4 further comprising adeployment control device which controls the deployment of the elasticroll out boom as the elastic roll out boom extends into the deployedconfiguration.
 6. The deployable structure of claim 5 wherein thedeployment control device comprises (i) a stabilizer arm and a boomcontrol roller, wherein the stabilizer arm connects the boom controlroller about the longitudinal axis of the mandrel, and (ii) a rotarydamping mechanism, wherein the rotary damping mechanism is connectedin-line with the longitudinal axis of the mandrel, wherein the rotarydamping mechanism controls the rate of mandrel rotation duringdeployment of the elastic roll out boom as the elastic roll out boomextends into the deployed configuration.
 7. The deployable structure ofclaim 5 wherein the deployment control device comprises (i) a stabilizerbar, a stabilizer arm, and a boom control roller, wherein the stabilizerarm connects the boom control roller to the longitudinal axis of themandrel, and (ii) a deployment lanyard and a rotating pulley, whereinthe deployment lanyard has a first end and a second end opposite saidfirst end, wherein the first end of the deployment lanyard is attachedto the stabilizer bar, wherein the second end of the deployment lanyardis attached to the rotating pulley, and wherein the rotating pulley isattached to the yoke support structure such that unidirectional boomdeployment is effected.
 8. The deployable structure of claim 4, furthercomprising a flexible photovoltaic blanket, wherein the flexiblephotovoltaic blanket is substantially planar having a first end and asecond end, wherein the flexible photovoltaic blanket is attached at thefirst end to the mandrel, and at the second end to the yoke supportstructure.
 9. The deployable structure of claim 8, wherein the elasticroll out boom and the flexible photovoltaic blanket are capable of beingrolled onto the mandrel simultaneously into the stowage configuration.10. A deployable structure comprising: a. an elastic roll out boomcomprising a thin-wall tubular, elongated structure, of afiber-composite layup material having internal strain energy, theelastic roll out boom having a stowage configuration for transport and adeployed configuration in which the elastic roll out boom is fullyextended, the elastic roll out boom having a first end, a second endopposite said first end, wherein a longitudinal axis is defined by thefirst end and the second end when the elastic roll out boom is in thedeployed configuration, wherein only the internal strain energy of thefiber-composite layup material causes extension of the elastic roll outboom from the stowage configuration to the deployed configuration; b. amandrel, the mandrel being a substantially cylindrical structure havinga longitudinal axis upon which the mandrel is able to rotate, whereinthe longitudinal axis of the elastic roll out boom is perpendicular tothe longitudinal axis of the mandrel, and the elastic roll out boom iscapable of being reversibly flattened in cross-section and rolled uponthe mandrel into the stowage configuration; c. a yoke support structure,the yoke support structure providing a fixed base for deployment of theelastic roll out boom, wherein the first end of the elastic roll outboom is attached to the mandrel and the second end is attached to theyoke support structure; and d. a flexible photovoltaic blanket, whereinthe flexible photovoltaic blanket is substantially planar having a firstend and a second end, wherein the flexible photovoltaic blanket isconnected at the first end to the mandrel, and at the second end to theyoke support structure, wherein the flexible photovoltaic blanketdeploys simultaneously with the elastic roll out boom from the stowageconfiguration to the deployed configuration.
 11. The deployablestructure of claim 10 wherein the flexible photovoltaic blanket is notattached to the elastic roll out boom.
 12. The deployable structure ofclaim 10 wherein the fiber-composite layup material is primarilyunidirectional.
 13. The deployable structure of claim 10 furthercomprising a deployment control device which controls the deployment ofthe elastic roll out boom as the elastic roll out boom extends into thedeployed configuration.
 14. The deployable structure of claim 13 whereinthe deployment control device comprises: (i) a stabilizer arm and a boomcontrol roller, wherein the stabilizer arm connects the boom controlroller about the longitudinal axis of the mandrel, and (ii) a rotarydamping mechanism, wherein the rotary damping mechanism is connectedin-line with the longitudinal axis of the mandrel, wherein the rotarydamping mechanism controls the rate of mandrel rotation duringdeployment of the elastic roll out boom as the elastic roll out boomextends into the deployed configuration.
 15. The deployable structure ofclaim 13 wherein the deployment control device comprises: (i) astabilizer bar, a stabilizer arm and a boom control roller, wherein thestabilizer arm connects the boom control roller to the longitudinal axisof the mandrel, and (ii) a deployment lanyard and a rotating pulley,wherein the deployment lanyard has a first end and a second end oppositesaid first end, wherein the first end of the deployment lanyard isattached to the stabilizer bar and the second end of the deploymentlanyard is attached to the rotating pulley, and the rotating pulley isattached to the yoke support structure.
 16. The deployable structure ofclaim 13 wherein the flexible photovoltaic blanket has a stowageconfiguration as a stowed roll having a diameter, wherein the deploymentcontrol device comprises (i) a stabilizer bar, a stabilizer arm and aboom control roller, wherein the stabilizer arm connects the boomcontrol roller to the longitudinal axis of the mandrel, (ii) africtionless tensioned containment strap, and a strap cross bar, whereinthe frictionless tensioned containment strap has a first end and asecond end, the first end connected to the stabilizer bar, the secondend being connected to the strap cross bar, wherein the frictionlesstensioned containment strap surrounds the stowed roll, (iii) wherein thefrictionless tensioned containment strap controls the stowed rolldiameter during deployment to the deployed configuration.
 17. Thedeployable structure of claim 10, further comprising a lateral blanketsupport structure, a base preload platen, and a tip preload platen,wherein the lateral blanket support structure is attached to the mandrelwherein the flexible photovoltaic blanket is attached at the first endto the lateral blanket support structure, and at the second end to theyoke support structure, wherein the flexible photovoltaic blanket isstowable in the stowage configuration between the tip preload platen andthe base preload platen as a z-fold flat package.
 18. The deployablestructure of claim 17, further comprising a lateral blanket mandrelsystem comprising a system of lanyards and pulleys, and an auxiliaryelectric motor, wherein the flexible photovoltaic blanket is attached atthe first end to the lateral blanket support structure and at the secondend to the yoke support structure, wherein the lateral blanket mandrelsystem powers extension of the flexible photovoltaic blanket to thedeployed configuration.